<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style>
			#box{
				width:500px;
				height:300px;
				border:4px red solid;
			}
		</style>
		<script>
			window.onload=function(){
				var btn=document.getElementById("btn");
				var box=document.getElementById("box");
				btn.onclick=function(){
					//创建新标签
					var newfile=document.createElement('input');
					newfile.setAttribute('type','file');
					//将新上传框增加到box
					box.appendChild(newfile);
				}
			}
		</script>
	</head>
	<body>
		<input type="button" value='点击增加上传框' id='btn' />
		<br />
		<div id='box'>
			<input type="file" />
		</div>
	</body>
</html>
